It is well known to utilize remote elevator monitoring systems (REMs) for monitoring operating conditions in individual elevators in widely diverse locations. Examples of such a system are described in U.S. Pat. No. 4,568,909 and 4,622,538, briefly illustrated in FIG. 1 herein. Each monitors individual elevators in remotely located buildings 12 (therein referred to as REM buildings), transmits alarm and performance information to associated local monitoring centers 14, and retransmits the alarm and performance information from the local centers to a central monitoring center 16, the purposes of which are fully set forth in the aforementioned patents and not germane herein. Each of the buildings 12 includes a master data processing system 18 and one or more slave data processing units 20 which together gather significant information about corresponding elevators and elevator shafts. The slaves 20 communicate with the master over lines 22, which permits locating the master 18 in an environment within the building which is less severe than the elevator machine rooms. Each master 18 communicates through a modem 24 and over ordinary community telephone lines to a modem 26 within the local monitoring center 14. The modem 26 exchanges information with a local data processor 28, which informs service personnel of conditions in all of the associated elevators being monitored, by means of displays (not shown) and/or a printer 30.
The REMS of the type described in said patents have evolved with increasing sophistication and have found widespread use. The value of them includes being able to provide alarms quickly for response by local service personnel, as well as providing other information indicative of impending degradation of the elevator system or potential harm or inconvenience to the passengers (referred to herein as "alerts"). And such systems allow the transfer of significantly more information, to assist in diagnosing the total situation so that a correct response can be made.
The local monitoring centers 14 typically service buildings of a small city, or of a particular sector of a large city, which is suited to the capability of service personnel to handle required calls indicated thereby. Since a local monitoring center 14 can be connected over ordinary phone lines to literally any building in its area, the services afforded thereby are readily available to all of the buildings in the area, subject to the availability of suitable phone lines.
In the usual case, the modem 24 in each building 12 is connected to its own, dedicated phone line over which it will communicate with the modem 26 of the local monitoring center 14. Some service customers deem the dedication of a phone line to the relatively infrequent use of an elevator monitoring system as being too extravagant. In some locations, particularly in countries other than the United States, phone lines are not only extremely expensive, but difficult to obtain, requiring extremely long waiting times for assignment of a line. The significant advantages of a REMS is therefore lost for want of a phone line.